SDCA2- Spongy degeneration with cerebellar ataxia
SDCA2 is a form of spongy degeneration with cerebellar ataxia, an inherited disorder which affects the Belgian Shepherd Dog. It is part of a wider group of disorders known as inherited cerebellar ataxia which represents a wide group of heterogeneous neurodegenerative disorders characterized by progressive degeneration of cerebellum and extracerebellar structures. In humans, inherited ataxia shows various modes of inheritance, with autosomal dominant inheritance as the most prevalent. In dogs, a genetic basis of cerebellar ataxias has been described for only some autosomal recessive inherited disorders.
Characteristics and symptoms
Affected puppies start to show symptoms around 4 weeks of age. Symptoms include generalized ataxic gait, seizures, and pacing as well as circling and central blindness. These clinical signs showed very rapid progression. Affected puppies may die during a seizure. Histopathological examination revealed vacuolation of the neuropil, and neuronal necrosis and severe gliosis in the spinal cord. In the hippocampus, neuronal necrosis and presence of hypertrophic astrocytes with vesicular nuclei are present, similar as in Alzheimer type II cells.
SDCA2, Spongy degeneration with cerebellar ataxia in Belgian Shepherd dog is caused by a mutation in exon 2 of the ATP1B2 gene, which encodes a subunit of Na+/K+-ATPase, an enzyme crucial for signal transduction.
The disorder is inherited in an autosomal recessive pattern. A dog can be clear, carrier or affected. Carriers of the gene are heterozygous and do not develop the disease’s symptoms. When mating two carrier dogs, each future cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
Mauri, N., Kleiter, M., Dietschi, E., Leschnik, M., Högler, S., Wiedmer, M., … Leeb, T. (2017). A SINE Insertion in ATP1B2 in Belgian Shepherd Dogs Affected by Spongy Degeneration with Cerebellar Ataxia (SDCA2). G3: Genes|Genomes|Genetics, 7(8), 2729–2737. http://doi.org/10.1534/g3.117.043018